Abstract: In the Tunisian highland steppes the desert ant species Cataglyphis bicolor (Fabricius, 1793) and C. mauritanica (Emery, 1906) share common microhabitat preferences. Endowed with equally sized workers they exhibit the same daily activity patterns within equally sized foraging areas, where they scavenge for the same type and size of food items. Neither do they establish food territories nor do their foragers avoid the vicinity of neighbouring nests, be they conspecific or allospecific. Due to this strong overlap of the ecological niches of C. bicolor and C. mauritanica the question arises whether the coexistence of the two species is a stable one, or whether it just reflects a temporary episode within a colonization process recurring time and again in instable environments.